Field of the Invention
The invention relates to a heat exchanger and to an arrangement of heat exchangers.
Description of the Background Art
Vehicle refrigerant circuits, in which a condenser is employed in order to cool and condense the refrigerant, which is brought to a high pressure by a compressor, are used in climate control systems in motor vehicles. The thus condensed refrigerant is then evaporated in an evaporator, which is connected downstream of the condenser, so that because of a heat exchange between air, flowing through the evaporator, and the refrigerant, the air is cooled in order to be able to control the temperature of or cool the motor vehicle interior.
To increase the evaporator capacity, the refrigerant is therefore cooled more greatly in the condenser than is necessary for mere condensation. As a result, the inlet enthalpy in the evaporator is reduced further. When coolant-cooled condensers, which are also called indirect condensers, are used, the waste heat of the condenser is given off not directly to the air, but to a coolant, connected there between, in a coolant circuit, whereby as a result the lowest temperature of the coolant in the coolant circuit is much higher than in air-cooled condensers, because the employed coolant in the coolant circuit has a much higher coolant temperature than the ambient air that cools the refrigerant in air-cooled condensers. This means that in these so-called indirect condensers the inlet enthalpy at the evaporator has not declined so far that performance losses in the evaporator result.
The air-cooled condenser does not have these problems, but it requires a relatively large amount of installation space in the front area of the vehicle, which in modern motor vehicles is not always available or cannot always be made available to the necessary extent.
The air-cooled condensers are also beset with the problem that they are often damaged in accidents with front damage to the vehicle and the refrigerant can then escape, whereby in the case of modern chemical refrigerants this can result in considerable costs. Efforts are therefore made to remove the air-cooled condenser from the front area of the motor vehicle in order to protect it in an accident situation. However, this cannot be done with air-cooled technology, because, for example, sufficient air for cooling the refrigerant is not available in another position in the engine compartment. Therefore, it is advantageous that the condenser is operated with coolant cooling.
WO 2004/085810, which corresponds to U.S. Pat. No. 8,051,809, proposes as a solution to this problem the provision of a subcooler, which is operated with a coolant of a low-temperature cooler. This has the disadvantage, however, of a very high interconnection complexity for providing the low-temperature coolant and often results in a rather poor controllability of the entire system.